Electromotive device



April 25, 1950 w. s. MACDONALD ELECTROMOTIVE DEVICE Filed Aug. 22. 1945 A? 39/ Ml M 2am 1 JWJZQ 1M2};

Patented Apr. 25, 1950 ELECTROMOTIVE DEVICE Waldron Shapleigh Macdonald, Montgomery County, Md.

Application August 22, 19%, Serial No, 611,990

r claims, 3

This invention relates to electromotive devices. such as motors, relays, and the like, consisting essentially of means for establishing a magnetic field, and an armature supported for movement within that field. It is the principal object of the invention to provide a device of this character having exceedingly low current consumption which may be simply controlled and operated from a source of supply which is capable oi delivering only very low power.

It has heretofore been proposed to employ a permanent magnet to provide the magnetic held of an electric motor, the direction of rotation of the motor armature being reversed by appropriate control of the current supplied to the armature windings. in accordance with the present invention, the motor field is established by an electromagnet having a core which is capable of magnetization by the application to a core winding of an electric impulse of duration which is short as compared to the period of magnetiaation, the core retaining its magnetism, fcllowing such energization, until demagnetized by the application to the winding of an impulse of opposite polarity and appropriate magnitude; by the application of an impulse of opposite polarity and greater magnitude, or by a succession of smaller impulses, the core may be reversely magnetized to initiate reverse movement of the armature. Thespeed and power of the motor may be varied selectively by successive impulses in the same or opposite direction, as the case may be.

The invention finds application in many fields, and is of special value when applied to small relays such as those employed in telephone systems and the like. Thus, a relay constructed in accordance with the present invention and having an impulse magnetizable core will remain energized without further current consumption until deenergized by an impulse of opposite polarity, and the impulse may be derived from the discharge of a condenser, previously slowly charged from a low power source, so as to minimize equipment and space requirements.

For convenience in describing and claiming the invention, the field magnet will be considcred stationary and the armature movable. It

will be apparent, however, that the movable element may be constituted by the magnetizable core, reversal of the parts being contemplated in the application of the invention. Furthermore, both elements of the device may be magnetizable if desired.

Further objects and features of the invention will be apparent from the following description all taken in connection with the accompanying drawings, in which Figure l is a perspective view of one form of motor to which the invention may be applied;

Figure 2 is a perspective view of a relay embodying the invention;

Figure 3 is a wiring diagram illustrating one application of the principles of the invention; and

Figure 4 is a wiring diagram illustrating a modification of the form of the invention shown in Figure 3.

For convenience in describing the invention, and in order to facilitate an understanding thereof, reference is made herein to the embodiments illustrated in the drawing and specific language is employed to describe the same. t will nevertheless be appreciated that no limitation of the scope of the invention is thereby intended, such alterations and modifications of the illustrated structure as would occur to one skilled in the art being contemplated as part of the invention.

Figure 1 shows a simple form of direct current motor including an armature ID, a commutator ii, and brushes It, the armature and commutator being suitably supported for rotation in a magnetic field. The field is provided by a core l5, and a winding l6 having leads I! is associated with the core.

As hereinbefore explained, it is a feature of the invention that the field core is magnetized by a. current impulse, and demagnetized or magnetized reversely by a current impulse or impulses flowing through the winding in the Opposite direction. It is therefore essential that the core be formed of a suitable magnetic material capable of retaining enough residual magnetism to provide the desired field strength. It is also preferable to employ a laminated core, in order to prevent the large eddy currents which would otherwise flow when the field winding is energized, and the material of the core should therefore be of such a nature that it may conveniently be rolled into sheet form. There are several well known materials having the desired characteristics, and the selection of a suitable material oil'ers no difiiculty to those skilled in this art. The alloy sold under the trade name Vicalloy is one such material, this alloy comprising cobalt and iron, aiiording the necessary magnetic qualities, and vanadium to facilitate mechanical working. Where the eddy current loss is of secondary importance, the workability of the material may be of less importance. For instance, where a high field strength is paratrade name Alnico may be employed. 7

Figure 2 shows the application of the invention to a relay, having a magnet core I! with which is associated a winding i6 having leads i1, the core I6 being preferably formed in the manner described above with reference to the motor core I6. An armature is pivoted to the core I 5', the core and the armature being provided with cooperating contacts 2| and 22, mounted on blocks of suitable insulating material. These contacts are engaged when the core is magnetized, by energization of the winding l6, a current impulse of short duration suflicing to impart sustained magnetization to the core, and remain engaged when the magnetizing current is interrupted. The application'to the winding I6 of a current impulse of short duration in the opposite direction demagnetizes the core l5 and releases the armature 20, permitting the contacts 2| and 22 to open. Armature 2|] may either be actuated by gravity or spring biased to the opened position.

It will be appreciated that the structural details of the motor and relay hereinbei'ore described tormno essential part of the instant invention. Either of these devices may bereplaced by devices differing widely therefrom, it being necessary only that the core shall be formed of magnetic material such as that described, and shall be provided with a winding whereb it may be energized and deenergized by momentary current flow in either direction.

In Figure 3 of the drawing is shown a wiring diagram illustrating a simple form of circuit for applying current impulses to the magnet winding l6 of a relay such as shown in Figure 2, for the 4 required to demagnetise the core ll than to elect magnetization thereof, the condenser 36 may be of somewhat less capacity than the condenser 26; alternatively, the source 21 may develop less voltage than the-source Ill.

The term armature is used herein broadly to describe any member displaceable in a magnetic field; thus the armature need not be permanently associated with the core as in a relay, but may constitute a work piece to be lifted or carried as in a magnetic chuck.

. In Figure 4 is illustrated in diagrammatic (cm a modified form of operating circuit, the controlled electromotive device being a motor such as the motor shown in Figure 1. having an armature I0 supplied by a current source 36, the field being established by the magnetization of core ll through the application 01' a current impulse to winding l6. The terminals I1 01 winding II are connected through a reversing switch 28 to condensers 40 and 4|, the selective discharge of which provides the current impulses tor magnetizing and demagnetizing the core it. In this arrangement the condensers are ermanently connected with the charging source 42, limiting resistors 44 and H being provided to prevent damage to the source following discharge 0! the respective condensers.

purpose of magnetizing the core i5 to attract and hold the armature 20. The core is magnetized through the discharge of a condenser 25 by displacing the movabl element of double throw switch 26 to the right as viewed on the drawing, the current impulse so created flowing in a circuit which includes resistor 21, provided for the purpose of damping oscillation. Switch 26 may be of any suitable type, such, for example, as a mercury switch. Following the application of the current impulse to the winding, the movable element of switch 26 may be thrown to the left to initiate recharging of condenser 25 from a source of supply, such at battery 30, resistor 3| being included in the circuit to limit current flow and prevent damage to the source.

Although the current impulse thus applied to the winding i6 is of short duration, the core i5 is magnetized andthe armature 20 is attracted to close the relay switch; the switch will stay closed for an indefinite period by reason of the residual magnetism of the core and without the application of further current to the winding.

For the purpose of opening the relay switch, a second impulse supplying circuit is provided, this circuit including a condenser ,35, a double throw switch 36 generally similar to switch 26, a source of supply 31, and a resistor 38. The condenser is charged while the movable element of switch 36' occupies the righthand position in which it is shown in Figure 3, the polarity of the sources 30 and 31 belng'such;that condenser 36 is charged reversely to condenser 25. When it is desired to open the contacts 2|, 22 of the relay switch, condenser 35 is discharged by displacing the movable element of the double throw switch 36 to the left, so as to discharge condenser 36 through winding I6, thereby demagnetizing core i6. Since a current impulse of somewhat less magnitude is The arrangement differs essentially from that shown in Figure 3 only as regards the means for controlling the discharge of the condensers. Thus, each of the condensers l0 and 4| discharges through an associated valve 45 of the gas conduction type, each valve having an anode l6, a cathode 41, and a control grid 46. The anode voltage for the valves is supplied by the source 42, and the valves are normally inoperative, either by reason of their characteristics or by the provision oi. a battery biasing the grids beyond cutoff. Either valve may be rendered conducting to discharge the associated condenser 40 or 4| by the application to the respective valve grid of a positive charge derived from a source 56, switch 6| being provided for the purpose of applyin the voltage of the source to the grid 46 through a coupling condenser 52, the charge subsequently draining from the grid through resistor 5| or a separate optional leakage resistor which may be associated with capacitor 52 as indicated at 62 of Fig. 4.

For example, closing of switch 5| at the left hand side of Figure 4 applies momentarily to the grid of the associated valve 45 a positive charge, the condenser lll discharging through the winding I6 in one direction to provide the current impulse necessary to magnetize the core l6, thereby initiating operation of the motor. When it is desired to stop the motor, the switch 6| at the right hand side of the figure is closed, and the associated valve 46 is rendered conducting to permit discharge of condenser 4| in the opposite direction through the winding l6, thereby demagnetizing the core ll. As in the previously described embodiment, the condenser I may be of lesser capacity than the condenser 46, the magnitude of the current impulse required to demagnetize the core being less than that required to establish magnetism in the first instance.

In the event it is desired to rotate the motor in the reverse direction, the reversing switch 26 is actuated to reverse the connections between the' condensers l0 and 4| and the winding l6. The core may then be magnetized in the reverse direction by discharge of condenser ll and demosnetized by discharge oi condenser in the man ner hereinbefore described.

As hereinbei'ore pointedout, either the movable or the stationary member of the device may be magnetized to achieve the results herein described, and in some instances it may be con venient to associate a winding with both the movable and stationary elements for the purpose of magnetizing either or both. Reference herein to a winding is intended, 01' course, to include a multiple winding in which different winding sections are energized to effect reverse magnetization of the core.

It will be appreciated that the motor and relay illustrated herein are merely representative of electromotive apparatus to which the instant invention may be applied, and that the invention is not necessarily restricted in its use to such devices. On the contrary, the advantages of the invention may be realized in widely varying types of equipment embodying relatively movable ele= ments, the motion of which is initiated by the establishment of a magnetic field. The invention makes possible the actuation of such devices with minimum power, and the accumulation of the power required to set up the initial electromagnetic field may be accomplished by drainage from a low power source over a considerable period of time.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:'

1. In an electromotive device, the combination with an armature, a permanently magnetizable field core, and a core winding, of means operable to apply to said winding a current impulse of suificient magnitude to effect sustained magnetization of said core following the application of said impulse, and to apply to said winding a current impulse of opposite polarity and of suificient magnitude to effect substantial demagnetization of said core, said means comprising a condenser, a source for charging said condenser, and means for discharging said condenser through said core winding, said last named means including a thermionic valve having the anode circuit thereof in series with said condenser and said winding. said valve being normally non-conducting, and means for supplying to the grid of said valve a positive charge to permit discharge of the condenser through the valve and said winding.

2. In an electromotive device, the combination with an armature, a permanently magnetizable field core, and a core winding, of means operable to apply to said winding a current impulse of sufiicient magnitude to eilect sustained magnetization of said core following the application of said impulse, and to apply to said winding a current impulse of opposite polarity and of sufficient magnitude to effect substantial demagnetization of said core, said means comprising a pair of condensers, means for charging said condensers, and devices for selectively discharging said condensers through said core winding to provide the said current impulses of opposite polarity, said devices comprising a pair of thermionic valves, one of said valves being arranged in series with each of said condensers and with said winding, said one of said valves being normally non= conducting, and means for selectively supplying to the grid of either of the valves a positive charge to permit discharge of the associated condenser through the selected valve and said core winding.

3. A motor having a field core composed of a magnetizable alloy having a high remanence and an armature in the magnetic circuit of the core, an armature winding, means for applying current to said armature winding, an energizing winding associated with said field core, means for selectively applying to said energizing wind-= ing an impulse to magnetize said core and initiate operation oi said motor, and means for selectively applying an impulse of opposite polarity to said winding to demagnetize said core thereby to stop the motor.

4. A motor having a field core composed of a magnetizable alloy having a high remanence and an armature in the magnetic circuit of the core, an armature winding, means for applying current to said armature winding, an energizing winding associated with said field core, means tor selectively applying to said energizing winding an im= pulse to magnetize said core and initiate operation of said motor, and means for selectively applying at least one impulse of opposite polarity to reversely magnetize said core thereby to re verse the motor.

5. In an electromotive device, the combination with an armature, a permanently magnetizaole field core, a core winding, and a field energizing current source, of switching apparatus operable to apply to said winding a current impulse oi suflicient magnitude to effect sustained ma netization of said core following the application of said impulse, and to apply to said winding a current impulse of opposite polarity likewise oi suflicient magnitude to effect sustained reverse magnetization oi. the core following the applica tion of the impulse of opposite polarity; said switching apparatus comprising a pair of condensers, a network for charging said condensers from said source, and a network for selectively discharging said condensers through said winding to provide said current impulses of opposite polarity, said discharging network comprising a pair of vacuum tubes, one of said tubes being arranged in series with each of said condensers and with said winding, and means for selectively supplying to the control electrode of either of the tubes a potential permitting discharge of the associated condenser through the selected tube and the winding.

6. A motor comprising a field core of a mag netizable alloy having a high remanence, an armature in the magnetic circuit of said core, an armature winding, a field winding associated with said core, and a selectively energizing network for said field winding, said network. including a capacitor, a source for charging said capacitor, and switching apparatus for charging the capacitor and for applying a discharge from the capacitor to said field winding in a selected sense, whereby the motor can be operated in either sense upon application 01' the ca acitor dischar e establishing a permanent magnetic circuit until a discharge in opposite sense is a lied.

'7. In an electromotive device, the combination with an armature, a permanently magnetizable field core, and a core winding, of means operable to apply to said winding a current impulse oi. sufficient magnitude to efiect sustained magnetization 01 said core following the ap lication of said impulse, said means comprising a capacitor, a source for charging said capacitor, and means for discharging said capacitor through said core winding, said discharging means including a vacuum tube having an anode circuit containing in series said capacitor and said winding, said tube being normally nonconducting, and means for supplying to the con- 7 8 trol electrode of said tube I. ositive charge Number Name Date initiating discharge of the capacitor through the 1,517,276 Brooke Dec. 2, 1924 valve and the winding. 1,824,132 Brown Apr. 12, 1927 WAIDRON SHAPLEIGH MACDONALD. 1,686,684 Davis Oct. 9, 1928 5 2,086,913 Kelly July 13, 1937 REFERENCES CITED 2,168,198 Frlnk Aug. 1, 1939 The following references are of record in the 2,170,594 1939 m of {hi patent: 2,277,579 Burger Mar. 24, 1942 2,353,733 Klemperer July 18, 1944 UNITED STATES PATENTS 10 FOREIGN PATENTS Number Name Date Number Country Date 8933 Chen July 1908 177,105 Switzerland Aug. 1, 1935 1,252,312 Warren Jan. 1, 1918 

